Device and process control in prior art electronics applications is generally achieved through special purpose circuitry using either simple gate logic or more complex microprocessor controllers. Such prior art devices typically are provided with switches to enable a user to manually initiate and control their various applications.
Generalized process control according to the prior art usually involves limited switching of electrical devices (e.g., a heater is turned on via a relay if temperature falls to a certain level). Such control strategies typically employ a device controller such as the 8255 programmable peripheral controller and the necessary hardware and software drivers. Thus, a logic state controls a semiconductor or mechanical relay which in turn switches a control voltage. Such a design is acceptable if the device to be controlled is engineered to respond to simple logic signals, or has simple control needs which can be accommodated through patterns of parallel data. However, such a control design is not acceptable for situations wherein control of large numbers of states is necessary, for control of analog applications, or for control of more complex switch strategies such as non-standard states and time-sensitive requirements.
In certain specialized fields there are standards and conventions governing the interaction among various devices engineered to conform to these standards. For example, IEEE 488 is a recognized standard for inter-device communication. Other examples of such standards are MIDI, which is used for control of musical instruments, and the proprietary CI-V standard published by ICOM America for the control of radio devices. Most devices which are part of such a configuration are generally also controllable through switches and similar means. Unfortunately, these existing standards and the associated control schemes require specialized engineering of the electrical device and adherence to rigorous pre-set standards.
Basic multiplexer techniques have been developed for applications such as the computer data/control bus, audio/video switching, and telephonic switching, however, such devices and the necessary software and processes have not been developed for general device and process control.
Because of the lack of a universal standard for device control, and because of the multiplicity of machine functions, intended users and disparate design strategies, a unifying approach for the control of electronic devices is unknown in the prior art.